Studies have shown that a significant proportion of vehicle accidents resulting in death are caused by sudden inattention of the vehicle driver. Such accidents are often severe since sudden inattention of the vehicle driver may cause frontal collisions or other severe types of accidents. The sudden inattention may be caused by a sudden severe medical condition, such as fainting, heart attack, etc., or by the driver falling asleep. In cases where the sudden inattention of the driver is caused by a sudden severe medical condition, the medical condition of the driver itself may need immediate medical attention, which further explains the severeness of these types of accidents. If one could recognize the sudden inattention of vehicle drivers and perform actions in response thereto, a large proportion of these accidents could be avoided. However, the sudden inattention is difficult to detect and actions have to be taken within a short period of time if an accident is to be avoided. Also, a vehicle driver assist arrangement must not unnecessarily intervene or alert the driver. The document DE 10024227 A1 describes electronic monitoring of the driver's eyes and/or eyelid activity and generating an alarm signal if tiredness is electronically detected. Even if such electronic monitoring of the driver's eyes and/or eyelid activity could recognize some of the cases where sudden inattention of vehicle drivers occur, such electronic monitoring does not satisfactory recognize sudden inattention of the driver, and are therefore unable of satisfactory assisting the vehicle driver. Thus, there is a need for a vehicle driver assist arrangement with an improved accuracy in the assessment of vehicle driver attentiveness.